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  • methane  (1)
  • pyrite  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    The selectivity of a sequential extraction procedure for the determination of iron oxyhydroxides andiron sulfides in lake sediments (1991)
    Springer
    Biodegradation 14 (1991), S. 193-208 
    Details
    ISSN: 1572-9729
    Keywords: iron oxyhydroxide ; pyrite ; sediment ; sequential extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A popular sequential extraction procedure (Tessier et al. 1979) designed t o extract metals partitioned in various sediment phases, was evaluated for its selectivity. Amorphous FeOOH, FeS, and FeS2 were added separately to natural lake sediments and sequentially extracted. The selectivity of the sequential procedure for the added solid phases was evaluated by determining the difference in the mass of Fe extracted from treated and control sediments. In the experiments where sulfide minerals were added, total S was measured in the residual solids in order to confirm selectivity of the method. Concentrations of total carbon remaining in the solid phase after each extraction step were also measured to determine the selectivity of the sequential procedure for carbon. The procedure was moderately selective for Fe added as FeOOH; a mean of 77 ± 12% (p 〈 0.05) of the Fe added was extracted in the step designed to reduce Fe-Mn oxyhydroxides. In experiments where FeS was added, a mean of 69 ± 11% (p 〈 0.05) of the Fe added as FeS was extracted in the fraction designed to oxidize sulfides and organic matter. Approximately 25% of the Fe added as FeS may have been extracted prematurely. Although less precise, total S analyses confirmed that much of the FeS was extracted in the oxidation step, yielding 104 ± 87% (p 〈 0.05) of the S added as FeS. The procedure was highly selective for FeS2; 92 ± 14% (p 〈 0.05) of the Fe added as pyrite was extracted in the sulfide extraction step. Extraction of 80 ± 54% (p 〈 0.05) of S added as pyrite confirmed that FeS2 were selectively extracted in the sulfide extraction step. Carbon in the sediments was also selectively extracted in the oxidation step (77 ± 2.4% of total C; p 〈 0.05). The applications and limitations of sequential extraction procedures as limnological research tools are discussed in light of our results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00000807
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A three-year study of controls on methane emissions from two Michigan peatlands (1994)
    Springer
    Biogeochemistry 27 (1994), S. 35-60 
    Details
    ISSN: 1573-515X
    Keywords: bogs ; methane ; peatlands ; wetlands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract We investigate temporal changes in methane emissions over a three-year period from two peatlands in Michigan. Mean daily fluxes ranged from 0.6–68.4 mg CH4 m−2d−1 in plant communities dominated by Chamaedaphne calyculata, an eficaceous shrub, to 11.5–209 mg CH4 m−2d−1 in areas dominated by plants with aerenchymatous tissues, such as Carex oligosperma and Scheuchzeria palustris. Correlations between methane flux and water table position were significant at all sites for one annual cycle when water table fluctuations ranged from 15 cm above to 50 cm below the peat surface. Correlations were not significant during the second and third annual periods with smaller water table fluctuations. Methane flux was strongly correlated with peat temperatures at −5 to −40 cm (r s = 0.82 to 0.98) for all three years at sites with flora acting as conduits for methane transport. At shrub sites, the correlations between methane flux and peat temperature were weak to not significant during the first two years, but were strong in the third year. Low rates of methane consumption (−0.2 to −1.5 mg CH4 m−2 d−1 ) were observed at shrub sites when the water table was below −20 cm, while sites with plants capable of methane transport always had positive net fluxes of methane. The methane oxidizing potential at both types of sites was confirmed by peat core experiments. The results of this study indicate that methane emissions occur at rates that cannot be explained by diffusion alone; plant communities play a significant role in altering methane flux from peatland ecosystems by directly transporting methane from anaerobic peat to the atmosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00002570
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    Paper (German National Licenses)
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